Is repentance from ideological disbelief valid for one who has fallen into it without excuse, and will this repentance be accepted such that the person becomes a Muslim in reality and in ruling, outwardly and inwardly, or is repentance in this case unavailing and the person remains an apostate?

Obsessive whispers (waswasah) must be treated by seeking Allah's help, supplicating, and completely turning away from thinking about them, while engaging in remembrance (dhikr) and beneficial deeds. Fleeting thoughts do not render one who detests them an unbeliever, nor does apostasy occur through mere possibility. Thus, whoever's Islam is established with certainty does not depart from it except with certainty. If someone falls into an act of disbelief (mukaffir) and asks scholars but the answer is delayed, they are not held accountable nor is their disbelief judged until proof is established against them and they persist in disbelief. If someone commits an act that nullifies Islam but then repents in their heart and prays, their Islam is affirmed, because prayer includes the two testimonies of faith (Shahadatayn).